Conventionally, there has been provided a compressor which includes a closed container, a compression element to be placed in the closed container, and a motor placed in the closed container to drive the compression element via a shaft (see JP S55-69180 U).
Conventionally, the compression element includes a front bearing and a rear bearing for supporting a shaft, and a cylinder to be placed between the front bearing and the rear bearing. The front bearing is placed closer to the motor than the rear bearing. The diameter of a front portion of the shaft supported by the front bearing is equal to the diameter of a rear portion of the shaft supported by the rear bearing.
A front annular groove and an annular-shaped front elastic portion positioned radially inward of the front annular groove are provided in a surface of the front bearing facing the cylinder, while a rear annular groove and an annular-shaped rear elastic portion positioned radially inward of the rear annular groove are provided in a surface of the rear bearing facing the cylinder.
The front elastic portion and the rear elastic portion are equal in width and height to each other, and it would the case that the rigidity of the front elastic portion and the rigidity of the rear elastic portion are equal to each other.
During operation of the above-described compressor, there may occur, from time to time, deflection of the shaft due to a gas load within the cylinder or other reasons, so that the shaft is brought into contact with the front bearing and the rear bearing. Even in such a case, the front elastic portion and the rear elastic portion are elastically deformed so that the contact of the shaft with the front bearing and the rear bearing can be made to be not point contact but plane contact. Thus, bearing pressures involved are reduced so that seizures are prevented.
In this connection, on condition that the diameter of the rear portion of the shaft is smaller than the diameter of the front portion of the shaft, deflection of the rear portion becomes larger than deflection of the front portion during the operation of the compressor.
In a case where a shaft having such a small-diameter rear portion is used in the above-described conventional compressor, since the rear elastic portion is equal in rigidity to the front elastic portion, it is impossible to increase the elastic deformation of only the rear elastic portion. As a result, the bearing pressure between the rear portion and the rear elastic portion is increased, causing seizures between the rear portion and the rear bearing.